Bioceramic coating, method of making and use thereof

ABSTRACT

Disclosed are a gradient bioceramic coating comprising a rare earth oxide, a broadband laser method for preparing the bioceramic coating, and the use of the bioceramic coating in the field of medical materials.

This application is a divisional application of U.S. patent applicationSer. No. 12/252,958, filed Oct. 16, 2008, now U.S. Pat. No. 8,206,843.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present application is directed to a bioceramic coating, a method ofmaking and use thereof. In particular, the present application isdirected to a gradient bioceramic coating comprising a rare earth oxide,a broadband laser method for preparing the bioceramic coating and theuse of the bioceramic coating in the field of medical materials.

2. Description of the Related Art

Bioceramic coating is an important part of biomedical materials andplays an important role in restoring defects of human sclerous tissuesand rebuilding the lost physiological functions. Generally, there aretwo kinds of techniques of preparing bioactive ceramic coatings, i.e.,dry process and wet process. The dry process is meant to carry outvarious reactions and depositions in gas phase. Examples of the dryprocess include plasma spraying, physical vapor deposition, chemicalvapor deposition, thermal spraying, laser cladding, ion injection, andthe like. The wet process is a technique that utilizes various reactionscarried out in liquid phase so as to deposit a coating on a substrate.Examples of wet process include sol-gel method, electrochemicaldeposition, self-assembling monolayer film method, and the like.

Laser cladding method is a technique which comprises precoating a mixedpowder of CaHPO₄ 2H₂O and CaCO₃ with a certain proportion on the surfaceof the substrate, and then cladding treating the surface of the metalsubstrate with a CO₂ laser processing system so that synthesis andcoating of hydroxyapatite (HA) on the surface of titanium alloy arecompleted in one step.

The mechanical properties of HA bioceramic coating mainly depends on thesintering density and microstructure of the final sintered product. Thetechnological parameters of broadband laser cladding can have asignificant effect on the microstructure and sinterability of thebioceramic coating.

BRIEF SUMMARY OF THE INVENTION

In a first aspect, the present application is directed to a gradientbioceramic coating, wherein the gradient bioceramic coating is preparedwith powdery titanium and powdery composite ceramics, wherein thepowdery composite ceramics are composed of powdery ceramics obtained bymixing CaHPO₄.2H₂O and CaCO₃, and a rare earth oxide added into thepowdery ceramics.

In a second aspect, the present application is directed to a gradientbioceramic coating, wherein the gradient bioceramic coating is preparedwith powdery titanium, powdery composite ceramics and hydroxyapatite,wherein the powdery composite ceramics are composed of powdery ceramicsobtained by mixing CaHPO₄.2H₂O and CaCO₃, and a rare earth oxide addedinto the powdery ceramics.

In a third aspect, the present application is directed to a method ofmaking a gradient bioceramic coating, comprising

(a) mixing and grinding powdery ceramics and a rare earth oxide to givea first mixture, and then mixing and grinding the first mixture andpowdery titanium to give a coating powder;

(b) mixing the coating powder and an adhesive to give a second mixture,and then prepressing the second mixture on the surface of a titaniumalloy TC4; and

(c) with broadband laser cladding techniques, cladding a first gradientlayer on the surface of the titanium alloy TC4, and then prepressing thecoating powders on the surface of the titanium alloy TC4 and cladding asecond gradient layer, and then prepressing the coating powders on thesurface of the titanium alloy TC4 again and cladding a third gradientlayer, so as to obtain the gradient bioceramics on the surface of thetitanium alloy TC4.

In a fourth aspect, the present application is directed to a gradientbioceramic coating, the gradient bioceramic coating is made according toa method comprising

(a) mixing and grinding powdery ceramics and a rare earth oxide to givea first mixture, and then mixing and grinding the first mixture andpowdery titanium to give a coating powder;

(b) mixing the coating powder and an adhesive to give a second mixture,and then prepressing the second mixture on the surface of a titaniumalloy TC4; and

(c) with broadband laser cladding techniques, cladding a first gradientlayer on the surface of the titanium alloy TC4, and then prepressing thecoating powders on the surface of the titanium alloy TC4 and cladding asecond gradient layer, and then prepressing the coating powders on thesurface of the titanium alloy TC4 again and cladding a third gradientlayer, so as to obtain the gradient bioceramics on the surface of thetitanium alloy TC4.

In a fifth aspect, the present application is directed to use of agradient bioceramic coating in defect-restoration and substitution ofhuman sclerous tissues.

DETAILED DESCRIPTION OF THE INVENTION

In the following description, certain specific details are included toprovide a thorough understanding of various disclosed embodiments. Oneskilled in the relevant art, however, will recognize that embodimentsmay be practiced without one or more of these specific details, or withother methods, components, materials, etc.

Unless the context requires otherwise, throughout the specification andclaims which follow, the word “comprise” and variations thereof, suchas, “comprises” and “comprising” are to be construed in an open,inclusive sense, which is as “including, but not limited to”.

Reference throughout this specification to “one embodiment”, or “anembodiment”, or “in another embodiment”, or “some embodiments”, or “insome embodiments” means that a particular referent feature, structure,or characteristic described in connection with the embodiment isincluded in at least one embodiment. Thus, the appearance of the phrases“in one embodiment”, or “in an embodiment”, or “in another embodiment”,or “in some embodiments” in various places throughout this specificationare not necessarily all referring to the same embodiment. Furthermore,the particular features, structures, or characteristics may be combinedin any suitable manner in one or more embodiments.

It should be noted that, as used in this specification and the appendedclaims, the singular forms “a”, “an”, and “the” include plural referentsunless the content clearly dictates otherwise. Thus, for example,reference to a solvent containing “a substance having polyhydroxy and/orpolyamino groups” includes a single substance having polyhydroxy and/orpolyamino groups, or two or more substances having polyhydroxy and/orpolyamino groups. It should also be noted that the term “or” isgenerally employed in its sense including “and/or” unless the contentclearly dictates otherwise.

In one aspect, the present application is directed to a gradientbioceramic coating, wherein the gradient bioceramic coating is preparedwith powdery titanium and powdery composite ceramics, wherein thepowdery composite ceramics are composed of powdery ceramics obtained bymixing CaHPO₄.2H₂O and CaCO₃, and a rare earth oxide added into thepowdery ceramics.

In some embodiments, on the basis of weight percent, the gradientbioceramic coating is prepared with about 60 to 0% of powdery titaniumand about 40 to 100% of powdery composite ceramics, wherein the powderycomposite ceramics are composed of powdery ceramics obtained by mixingabout 67 to 85% by weight of CaHPO₄.2H₂O and about 15 to 33% by weightof CaCO₃, and about 0.2 to 1.0% by weight of a rare earth oxide addedinto the powdery ceramics.

In some embodiments, on the basis of weight percent, the gradientbioceramic coating is prepared with about 80 to 10% of powdery titaniumand about 20 to 90% of powdery composite ceramics, wherein the powderycomposite ceramics are composed of powdery ceramics obtained by mixingabout 67 to 85% by weight of CaHPO₄.2H₂O and about 15 to 33% by weightof CaCO₃, and about 0.2 to 1.0% by weight of a rare earth oxide addedinto the powdery ceramics.

In some embodiments, the particle size of the powdery titanium is in therange of about 10 to 90 μm, the particle size of the powdery compositeceramics is in the range of about 20 to 60 μm, and the particle size ofthe rare earth oxide is in the range of about 0.1 to 10 μm.

In some embodiments, the particle size of the powdery titanium is in therange of about 20 to 80 μm, the particle size of the powdery compositeceramics is in the range of about 30 to 50 μm, and the particle size ofthe rare earth oxide is in the range of about 1 to 5 μm.

In some preferred embodiments, the particle size of the powdery titaniumis about 40 μm, the particle size of the powdery composite ceramics isabout 36 μm, and the particle size of the rare earth oxide is about 4μm.

In some preferred embodiments, the particle size of the powdery titaniumis about 20 μm, the particle size of the powdery composite ceramics isabout 30 μm, and the particle size of the rare earth oxide is about 1μm.

In some preferred embodiments, the particle size of the powdery titaniumis about 80 μm, the particle size of the powdery composite ceramics isabout 50 μm, and the particle size of the rare earth oxide is about 5μm.

In some embodiments, the powdery composite ceramics are composed ofpowdery ceramics obtained by mixing about 72 to 80% by weight ofCaHPO₄.2H₂O and about 20 to 28% by weight of CaCO₃, and about 0.4 to0.8% by weight of a rare earth oxide added into the powdery ceramics.

In some preferred embodiments, the powdery composite ceramics arecomposed of powdery ceramics obtained by mixing about 72% by weight ofCaHPO₄.2H₂O and about 28% by weight of CaCO₃, and about 0.4% by weightof a rare earth oxide added into the powdery ceramics.

In some preferred embodiments, the powdery composite ceramics arecomposed of powdery ceramics obtained by mixing about 78% by weight ofCaHPO₄.2H₂O and about 22% by weight of CaCO₃, and about 0.6% by weightof a rare earth oxide added into the powdery ceramics.

In some preferred embodiments, the powdery composite ceramics arecomposed of powdery ceramics obtained by mixing about 80% by weight ofCaHPO₄.2H₂O and about 20% by weight of CaCO₃, and about 0.8% by weightof a rare earth oxide added into the powdery ceramics.

Rare earth elements are a generic name of scandium, yttrium, andlanthanoid in Group IIIB of the Periodic Table of the Elements, whichinclude scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce),praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm),europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium(Ho), erbium (Er), thulium (Tm), ytterbium (Yb) and lutetium (Lu),wherein promethium is an artificial radioactive element.

In general, lanthanum, cerium, praseodymium, neodymium, promethium,samarium and europium are called light rare earth elements, whilegadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium andlutetium are called heavy rare earth elements. Light rare earth elementshave greater antithrombotic effects than those heavy earth elementshave. The radius of a light rare earth ion is closer to the radius of acalcium ion than that of a heavy rare earth ion. A rare earth ion hasone more positive charge than a calcium ion does. When a calcium ion issubstituted by a rare earth ion, rare earth ions effectively andcompetitively inhibits the effects of calcium ions during the bloodcoagulation process.

In some embodiments, a rare earth oxide that can be used in the presentapplication includes, but is not limited to, yttrium oxide (Y₂O₃),yttrium europium oxide ((Y,Eu)₂O₃), europium oxide (Eu₂O₃), lanthanumoxide (La₂O₃), cerous oxide (Ce₂O₃), ceric oxide (CeO₂), terbium oxide(Tb₄O₇) (including cerium terbium oxide ((Ce,Tb)_(x)O_(y)), lanthanumcerium terbium oxide ((La,Ce,Tb)_(x)O_(y)), lanthanum phosphateactivated by cerium and terbium: Ce(III), Tb(III)), samarium oxide(Sm₂O₃), neodminu oxide (Nd₂O₃), dysprosium oxide (Dy₂O₃), erbium oxide(Er₂O₃), ytterbium oxide (Yb₂O₃) and cerium zirconium oxide ((Ce,Zr)O₂).

In some preferred embodiments, the rare earth oxide is selected from thegroup consisting of lanthanum oxide (La₂O₃), ceric oxide (CeO₂) andyttrium oxide (Y₂O₃).

In some embodiments, the particle size of the powdery titanium is in therange of about 10 to 90 μm, the particle size of the powdery compositeceramics is in the range of about 20 to 60 μm, and the particle size ofthe rare earth oxide is in the range of about 0.1 to 10 μm, wherein thepowdery composite ceramics are composed of powdery ceramics obtained bymixing about 72 to 80% by weight of CaHPO₄.2H₂O and about 20 to 28% byweight of CaCO₃, and about 0.4 to 0.8% by weight of a rare earth oxideadded into the powdery ceramics.

In some preferred embodiments, the particle size of the powdery titaniumis in the range of about 20 to 80 μm, the particle size of the powderycomposite ceramics is in the range of about 30 to 50 μm, and theparticle size of the rare earth oxide is in the range of about 1 to 5μm, wherein the powdery composite ceramics are composed of powderyceramics obtained by mixing about 72 to 80% by weight of CaHPO₄.2H₂O andabout 20 to 28% by weight of CaCO₃, and about 0.4 to 0.8% by weight of arare earth oxide added into the powdery ceramics, and wherein the rareearth oxide is selected from the group consisting of lanthanum oxide(La₂O₃), ceric oxide (CeO₂) and yttrium oxide (Y₂O₃).

In some more preferred embodiments, the particle size of the powderytitanium is about 40 μm, the particle size of the powdery compositeceramics is about 36 μm, and the particle size of the rare earth oxideis about 4 μm, wherein the powdery composite ceramics are composed ofpowdery ceramics obtained by mixing about 78% by weight of CaHPO₄.2H₂Oand about 22% by weight of CaCO₃, and about 0.6% by weight of a rareearth oxide added into the powdery ceramics, and wherein the rare earthoxide is selected from the group consisting of lanthanum oxide (La₂O₃),ceric oxide (CeO₂) and yttrium oxide (Y₂O₃).

In some more preferred embodiments, the particle size of the powderytitanium is about 40 μm, the particle size of the powdery compositeceramics is about 36 μm, and the particle size of the rare earth oxideis about 4 μm, wherein the powdery composite ceramics are composed ofpowdery ceramics obtained by mixing about 78% by weight of CaHPO₄.2H₂Oand about 22% by weight of CaCO₃, and about 0.6% by weight of a rareearth oxide added into the powdery ceramics, and wherein the rare earthoxide is lanthanum oxide (La₂O₃).

In some more preferred embodiments, the particle size of the powderytitanium is about 40 μm, the particle size of the powdery compositeceramics is about 36 μm, and the particle size of the rare earth oxideis about 4 μm, wherein the powdery composite ceramics are composed ofpowdery ceramics obtained by mixing about 78% by weight of CaHPO₄.2H₂Oand about 22% by weight of CaCO₃, and about 0.6% by weight of a rareearth oxide added into the powdery ceramics, and wherein the rare earthoxide is ceric oxide (CeO₂).

In another aspect, the present application is directed to a gradientbioceramic coating, wherein the gradient bioceramic coating is preparedwith powdery titanium, powdery composite ceramics and hydroxyapatite,wherein the powdery composite ceramics are composed of powdery ceramicsobtained by mixing CaHPO₄.2H₂O and CaCO₃, and a rare earth oxide addedinto the powdery ceramics.

In some embodiments, on the basis of weight percent, the gradientbioceramic coating is prepared with about 60 to 0% of powdery titanium,about 40 to 100% of powdery composite ceramics and about 0 to 50% ofhydroxyapatite, wherein the powdery composite ceramics are composed ofpowdery ceramics obtained by mixing about 67 to 85% by weight ofCaHPO₄.2H₂O and about 15 to 33% by weight of CaCO₃, and about 0.2 to1.0% by weight of a rare earth oxide added into the powdery ceramics.

In some embodiments, the particle size of the powdery titanium is in therange of about 10 to 90 μm, the particle size of the powdery compositeceramics is in the range of about 20 to 60 μm, the particle size of thehydroxyapatite is in the range of about 5 to 50 μm, and the particlesize of the rare earth oxide is in the range of about 0.1 to 10 μm.

In some embodiments, the particle size of the powdery titanium is in therange of about 20 to 80 μm, the particle size of the powdery compositeceramics is in the range of about 30 to 50 μm, the particle size of thehydroxyapatite is in the range of about 1 to 30 μm, and the particlesize of the rare earth oxide is in the range of about 1 to 5 μm.

In some preferred embodiments, the particle size of the powdery titaniumis about 40 μm, the particle size of the powdery composite ceramics isabout 36 μm, the particle size of the hydroxyapatite is about 15 μm, andthe particle size of the rare earth oxide is about 4 μm.

In some preferred embodiments, the particle size of the powdery titaniumis about 20 μm, the particle size of the powdery composite ceramics isabout 30 μm, the particle size of the hydroxyapatite is about 10 μm, andthe particle size of the rare earth oxide is about 1 μm.

In some preferred embodiments, the particle size of the powdery titaniumis about 80 μm, the particle size of the powdery composite ceramics isabout 50 μm, the particle size of the hydroxyapatite is about 30 μm, andthe particle size of the rare earth oxide is about 5 μm.

In some embodiments, the powdery composite ceramics are composed ofpowdery ceramics obtained by mixing about 72 to 80% by weight ofCaHPO₄.2H₂O and about 20 to 28% by weight of CaCO₃, and about 0.4 to0.8% by weight of a rare earth oxide added into the powdery ceramics.

In some preferred embodiments, the powdery composite ceramics arecomposed of powdery ceramics obtained by mixing about 72% by weight ofCaHPO₄.2H₂O and about 28% by weight of CaCO₃, and about 0.4% by weightof a rare earth oxide added into the powdery ceramics.

In some preferred embodiments, the powdery composite ceramics arecomposed of powdery ceramics obtained by mixing about 78% by weight ofCaHPO₄.2H₂O and about 22% by weight of CaCO₃, and about 0.6% by weightof a rare earth oxide added into the powdery ceramics.

In some preferred embodiments, the powdery composite ceramics arecomposed of powdery ceramics obtained by mixing about 80% by weight ofCaHPO₄.2H₂O and about 20% by weight of CaCO₃, and about 0.8% by weightof a rare earth oxide added into the powdery ceramics.

In some embodiments, a rare earth oxide that can be used in the presentapplication includes, but is not limited to, yttrium oxide (Y₂O₃),yttrium europium oxide ((Y,Eu)₂O₃), europium oxide (Eu₂O₃), lanthanumoxide (La₂O₃), cerous oxide (Ce₂O₃), ceric oxide (CeO₂), terbium oxide(Tb₄O₇) (including cerium terbium oxide ((Ce,Tb)_(x)O_(y)), lanthanumcerium terbium oxide ((La,Ce,Tb)_(x)O_(y)), lanthanum phosphateactivated by cerium and terbium: Ce(III), Tb(III)), samarium oxide(Sm₂O₃), neodminu oxide (Nd₂O₃), dysprosium oxide (Dy₂O₃), erbium oxide(Er₂O₃), ytterbium oxide (Yb₂O₃) and cerium zirconium oxide ((Ce,Zr)O₂).

In some preferred embodiments, the rare earth oxide is selected from thegroup consisting of lanthanum oxide (La₂O₃), eerie oxide (CeO₂) andyttrium oxide (Y₂O₃).

In some embodiments, the particle size of the powdery titanium is in therange of about 10 to 90 μm, the particle size of the powdery compositeceramics is in the range of about 20 to 60 μm, the particle size of thehydroxyapatite is in the range of about 5 to 50 μm, and the particlesize of the rare earth oxide is in the range of about 0.1 to 10 μm,wherein the powdery composite ceramics are composed of powdery ceramicsobtained by mixing about 72 to 80% by weight of CaHPO₄.2H₂O and about 20to 28% by weight of CaCO₃, and about 0.4 to 0.8% by weight of a rareearth oxide added into the powdery ceramics.

In some preferred embodiments, the particle size of the powdery titaniumis in the range of about 20 to 80 μm, the particle size of the powderycomposite ceramics is in the range of about 30 to 50 μm, the particlesize of the hydroxyapatite is in the range of about 1 to 30 μm, and theparticle size of the rare earth oxide is in the range of about 1 to 5μm, wherein the powdery composite ceramics are composed of powderyceramics obtained by mixing about 72 to 80% by weight of CaHPO₄.2H₂O andabout 20 to 28% by weight of CaCO₃, and about 0.4 to 0.8% by weight of arare earth oxide added into the powdery ceramics, and wherein the rareearth oxide is selected from the group consisting of lanthanum oxide(La₂O₃), ceric oxide (CeO₂) and yttrium oxide (Y₂O₃).

In some more preferred embodiments, the particle size of the powderytitanium is about 40 μm, the particle size of the powdery compositeceramics is about 36 μm, the particle size of the hydroxyapatite isabout 15 μm, and the particle size of the rare earth oxide is about 4μm, wherein the powdery composite ceramics are composed of powderyceramics obtained by mixing about 78% by weight of CaHPO₄.2H₂O and about22% by weight of CaCO₃, and about 0.6% by weight of a rare earth oxideadded into the powdery ceramics, and wherein the rare earth oxide isselected from the group consisting of lanthanum oxide (La₂O₃), cericoxide (CeO₂) and yttrium oxide (Y₂O₃).

In other aspects, the present application is directed to a method ofmaking a gradient bioceramic coating, comprising

(a) mixing and grinding powdery ceramics and a rare earth oxide to givea first mixture, and then mixing and grinding the first mixture andpowdery titanium to give a coating powder;

(b) mixing the coating powder and an adhesive to give a second mixture,and then prepressing the second mixture on the surface of a titaniumalloy TC4; and

(c) with broadband laser cladding techniques, cladding a first gradientlayer on the surface of the titanium alloy TC4, and then prepressing thecoating powders on the surface of the titanium alloy TC4 and cladding asecond gradient layer, and then prepressing the coating powders on thesurface of the titanium alloy TC4 again and cladding a third gradientlayer, so as to obtain the gradient bioceramics on the surface of thetitanium alloy TC4.

In some embodiments, the method of making a gradient bioceramic coatingfurther comprises mixing and grinding the coating powder obtained instep (a) and hydroxyapatite before carrying out the step (b) of mixingwith an adhesive.

In some embodiments, a first gradient layer prepressed on the surface ofthe titanium alloy TC4 is prepared with about 50 to 70% by weight ofpowdery titanium and about 50 to 30% by weight of powdery compositeceramics, a second gradient layer is prepared with about 10 to 40% byweight of powdery titanium and about 90 to 60% by weight of powderycomposite ceramics, and a third gradient layer is prepared with about100% by weight of powdery composite ceramics.

In some embodiments, a first gradient layer prepressed on the surface ofthe titanium alloy TC4 is prepared with about 50 to 70% by weight ofpowdery titanium and about 50 to 30% by weight of powdery compositeceramics, a second gradient layer is prepared with about 20 to 40% byweight of powdery titanium and about 80 to 60% by weight of powderycomposite ceramics, and a third gradient layer is prepared with about100% by weight of powdery composite ceramics.

In some preferred embodiments, a first gradient layer prepressed on thesurface of the titanium alloy TC4 is prepared with about 60% by weightof powdery titanium and about 40% by weight of powdery compositeceramics, a second gradient layer is prepared with about 30% by weightof powdery titanium and about 70% by weight of powdery compositeceramics, and a third gradient layer is prepared with about 50% byweight of hydroxyapatite and about 50% by weight of powdery compositeceramics.

In some embodiments, a first gradient layer prepressed on the surface ofthe titanium alloy TC4 is prepared with about 50 to 70% by weight ofpowdery titanium and about 50 to 30% by weight of powdery compositeceramics, a second gradient layer is prepared with about 20 to 40% byweight of powdery titanium and about 80 to 60% by weight of powderycomposite ceramics, and a third gradient layer is prepared with about 40to 60% by weight of hydroxyapatite and about 60 to 40% by weight ofpowdery composite ceramics.

In some preferred embodiments, a first gradient layer prepressed on thesurface of the titanium alloy TC4 is prepared with about 60% by weightof powdery titanium and about 40% by weight of powdery compositeceramics, a second gradient layer is prepared with about 30% by weightof powdery titanium and about 70% by weight of powdery compositeceramics, and a third gradient layer is prepared with about 50% byweight of hydroxyapatite and about 50% by weight of powdery compositeceramics.

In some embodiments, a first gradient layer prepressed on the surface ofthe titanium alloy TC4 is prepared with about 60 to 80% by weight ofpowdery titanium and about 40 to 20% by weight of powdery compositeceramics, a second gradient layer is prepared with about 30 to 50% byweight of powdery titanium and about 70 to 50% by weight of powderycomposite ceramics, and a third gradient layer is prepared with about 5to 15% by weight of powdery titanium and about 95 to 85% by weight ofpowdery composite ceramics.

In some preferred embodiments, a first gradient layer prepressed on thesurface of the titanium alloy TC4 is prepared with about 70% by weightof powdery titanium and about 30% by weight of powdery compositeceramics, a second gradient layer is prepared with about 40% by weightof powdery titanium and about 60% by weight of powdery compositeceramics, and a third gradient layer is prepared with about 10% byweight of powdery titanium and about 90% by weight of powdery compositeceramics.

In some embodiments, the thickness of the coating layer prepressed onthe surface of the titanium alloy TC4 is in the range of about 0.2 to0.8 mm.

In some embodiments, the thickness of the coating layer prepressed onthe surface of the titanium alloy TC4 is in the range of about 0.4 to0.6 mm.

In some embodiments, the thicknesses of a first gradient layer, a secondgradient layer and a third gradient layer prepressed on the surface ofthe titanium alloy TC4 may be identical or different.

In some preferred embodiments, all the thicknesses of a first gradientlayer, a second gradient layer and a third gradient layer prepressed onthe surface of the titanium alloy TC4 are 0.4 mm.

In some preferred embodiments, all the thicknesses of a first gradientlayer, a second gradient layer and a third gradient layer prepressed onthe surface of the titanium alloy TC4 are 0.5 mm.

In some preferred embodiments, all the thicknesses of a first gradientlayer, a second gradient layer and a third gradient layer prepressed onthe surface of the titanium alloy TC4 are 0.6 mm.

In some embodiments, the powdery composite ceramics and the rare earthoxide are mixed and ground over about 1 to 5 hours.

In some embodiments, the powdery composite ceramics and the rare earthoxide are mixed and ground over about 1 to 5 hours to give a firstmixture, and the first mixture and powdery titanium are mixed and groundover about 1 to 5 hours to give a coating powder.

In some embodiments, the technological parameters of broadband lasercladding are about 2.0 to 3.0 kW of output power P, about 100 to 200mm/min of scanning rate V, and about 16 to 30 mm×1 to 4 mm of spot sizeD.

In some preferred embodiments, the technological parameters of broadbandlaser cladding are about 2.5 kW of output power P, about 150 mm/min ofscanning rate V, and about 16 mm×2 mm of spot size D.

In some embodiments, the pressure used in prepressing the coatingpowders is in the range of about 40 to 60 kg/cm².

In some preferred embodiments, the pressure used in prepressing thecoating powders is about 50 kg/cm².

In some embodiments, the apparatuses used in the broadband lasercladding are TJ-HL-5000 5 kW CO₂ lasers, TJ-LTM-VI five-axis three axeslinkage laser processing numerical control machine, and JKF-6 laserbroadband scan mirror.

In some embodiments, an adhesive that can be used in the presentapplication includes, but is not limited to, chemical adhesives andbioadhesives.

Exemplary chemical adhesives include, but are not limited to,α-cyanoacrylates adhesives; polyurethanes adhesives; gelatins, such asGRF adhesives; organosilicons adhesives; alkyd esters adhesives, such assoya alkyds adhesives; poly(hydroxyethyl methacrylate) adhesives;polyvinyl emulsion adhesives; collodions adhesives; and the like.

Exemplary bioadhesives include, but are not limited to, thosebiomolecules that mediate attachment of cells, tissue, organs ororganisms onto non-biological surfaces like glass, rock etc. This groupof biomolecules includes marine mussel adhesive proteins, fibrin-likeproteins, spider-web proteins, plant-derived adhesives (resins),adhesives extracted from marine animals, and insect-derived adhesives(like resilins). Some specific examples of adhesives are: Fibrin;fibroin; Mytilus edulis foot protein (mefp1, “mussel adhesive protein”);other mussel's adhesive proteins; proteins and peptides withglycine-rich blocks; proteins and peptides with poly-alanine blocks; andsilks.

In some preferred embodiments, the adhesives used in the presentapplication are alkyd esters adhesives.

In some more preferred embodiments, the adhesives used in the presentapplication are soya alkyds.

In some even more preferred embodiments, the adhesives used in thepresent application are about 1 to 5 mL of soya alkyds.

In another aspect, the present application is directed to a gradientbioceramic coating, the gradient bioceramic coating is made according toa method comprising

(a) mixing and grinding powdery ceramics and a rare earth oxide to givea first mixture, and then mixing and grinding the first mixture andpowdery titanium to give a coating powder;

(b) mixing the coating powder and an adhesive to give a second mixture,and then prepressing the second mixture on the surface of a titaniumalloy TC4; and

(c) with broadband laser cladding techniques, cladding a first gradientlayer on the surface of the titanium alloy TC4, and then prepressing thecoating powders on the surface of the titanium alloy TC4 and cladding asecond gradient layer, and then prepressing the coating powders on thesurface of the titanium alloy TC4 again and cladding a third gradientlayer, so as to obtain the gradient bioceramics on the surface of thetitanium alloy TC4.

In some embodiments, the method of making a gradient bioceramic coatingfurther comprises mixing and grinding the coating powder obtained instep (a) and hydroxyapatite before carrying out the step (b) of mixingwith an adhesive.

In some embodiments, a first gradient layer prepressed on the surface ofthe titanium alloy TC4 is prepared with about 50 to 70% by weight ofpowdery titanium and about 50 to 30% by weight of powdery compositeceramics, a second gradient layer is prepared with about 10 to 40% byweight of powdery titanium and about 90 to 60% by weight of powderycomposite ceramics, and a third gradient layer is prepared with about100% by weight of powdery composite ceramics.

In some embodiments, a first gradient layer prepressed on the surface ofthe titanium alloy TC4 is prepared with about 50 to 70% by weight ofpowdery titanium and about 50 to 30% by weight of powdery compositeceramics, a second gradient layer is prepared with about 20 to 40% byweight of powdery titanium and about 80 to 60% by weight of powderycomposite ceramics, and a third gradient layer is prepared with about100% by weight of powdery composite ceramics.

In some preferred embodiments, a first gradient layer prepressed on thesurface of the titanium alloy TC4 is prepared with about 60% by weightof powdery titanium and about 40% by weight of powdery compositeceramics, a second gradient layer is prepared with about 30% by weightof powdery titanium and about 70% by weight of powdery compositeceramics, and a third gradient layer is prepared with about 50% byweight of hydroxyapatite and about 50% by weight of powdery compositeceramics.

In some embodiments, a first gradient layer prepressed on the surface ofthe titanium alloy TC4 is prepared with about 50 to 70% by weight ofpowdery titanium and about 50 to 30% by weight of powdery compositeceramics, a second gradient layer is prepared with about 20 to 40% byweight of powdery titanium and about 80 to 60% by weight of powderycomposite ceramics, and a third gradient layer is prepared with about 40to 60% by weight of hydroxyapatite and about 60 to 40% by weight ofpowdery composite ceramics.

In some preferred embodiments, a first gradient layer prepressed on thesurface of the titanium alloy TC4 is prepared with about 60% by weightof powdery titanium and about 40% by weight of powdery compositeceramics, a second gradient layer is prepared with about 30% by weightof powdery titanium and about 70% by weight of powdery compositeceramics, and a third gradient layer is prepared with about 50% byweight of hydroxyapatite and about 50% by weight of powdery compositeceramics.

In some embodiments, a first gradient layer prepressed on the surface ofthe titanium alloy TC4 is prepared with about 60 to 80% by weight ofpowdery titanium and about 40 to 20% by weight of powdery compositeceramics, a second gradient layer is prepared with about 30 to 50% byweight of powdery titanium and about 70 to 50% by weight of powderycomposite ceramics, and a third gradient layer is prepared with about 5to 15% by weight of powdery titanium and about 95 to 85% by weight ofpowdery composite ceramics.

In some preferred embodiments, a first gradient layer prepressed on thesurface of the titanium alloy TC4 is prepared with about 70% by weightof powdery titanium and about 30% by weight of powdery compositeceramics, a second gradient layer is prepared with about 40% by weightof powdery titanium and about 60% by weight of powdery compositeceramics, and a third gradient layer is prepared with about 10% byweight of powdery titanium and about 90% by weight of powdery compositeceramics.

In some embodiments, the thickness of the coating layer prepressed onthe surface of the titanium alloy TC4 is in the range of about 0.2 to0.8 mm.

In some embodiments, the thickness of the coating layer prepressed onthe surface of the titanium alloy TC4 is in the range of about 0.4 to0.6 mm.

In some embodiments, the thicknesses of a first gradient layer, a secondgradient layer and a third gradient layer prepressed on the surface ofthe titanium alloy TC4 may be identical or different.

In some preferred embodiments, all the thicknesses of a first gradientlayer, a second gradient layer and a third gradient layer prepressed onthe surface of the titanium alloy TC4 are 0.4 mm.

In some preferred embodiments, all the thicknesses of a first gradientlayer, a second gradient layer and a third gradient layer prepressed onthe surface of the titanium alloy TC4 are 0.5 mm.

In some preferred embodiments, all the thicknesses of a first gradientlayer, a second gradient layer and a third gradient layer prepressed onthe surface of the titanium alloy TC4 are 0.6 mm.

In some embodiments, the powdery composite ceramics and the rare earthoxide are mixed and ground over about 1 to 5 hours.

In some embodiments, the powdery composite ceramics and the rare earthoxide are mixed and ground over about 1 to 5 hours to give a firstmixture, and the first mixture and powdery titanium are mixed and groundover about 1 to 5 hours to give a coating powder.

In some embodiments, the technological parameters of broadband lasercladding are about 2.0 to 3.0 kW of output power P, about 100 to 200mm/min of scanning rate V, and about 16 to 30 mm×1 to 4 mm of spot sizeD.

In some preferred embodiments, the technological parameters of broadbandlaser cladding are about 2.5 kW of output power P, about 150 mm/min ofscanning rate V, and about 16 mm×2 mm of spot size D.

In some embodiments, the pressure used in prepressing the coatingpowders is in the range of about 40 to 60 kg/cm².

In some preferred embodiments, the pressure used in prepressing thecoating powders is about 50 kg/cm².

In some embodiments, the apparatuses used in the broadband lasercladding are TJ-HL-5000 5 kW CO₂ lasers, TJ-LTM-VI five-axis three axeslinkage laser processing numerical control machine, and JKF-6 laserbroadband scan mirror.

In some embodiments, an adhesive that can be used in the presentapplication includes, but is not limited to, chemical adhesives andbioadhesives.

In some preferred embodiments, the adhesives used in the presentapplication are alkyd esters adhesives.

In some more preferred embodiments, the adhesives used in the presentapplication are soya alkyds.

In some even more preferred embodiments, the adhesives used in thepresent application are about 1 to 5 mL of soya alkyds.

In other aspects, the present application is directed to use of agradient bioceramic coating in defect-restoration and substitution ofhuman sclerous tissues.

The term “implant” includes within its scope any device intended to beimplanted into the body of a vertebrate animal, in particular a mammalsuch as a human. Non-limiting examples of such devices are medicaldevices that replaces anatomy or restores a function of the body such asthe femoral hip joint; the femoral head; acetabular cup; elbow includingstems, wedges, articular inserts; knee, including the femoral and tibialcomponents, stem, wedges, articular inserts or patella components;shoulders including stem and head; wrist; ankles; hand; fingers; toes;vertebrae; spinal discs; artificial joints; dental implants;ossiculoplastic implants; middle ear implants including incus, malleus,stapes, incus-stapes, malleus-incus, malleus-incus-stapes; cochlearimplants; orthopaedic fixation devices such as nails, screws, staplesand plates; heart valves; pacemakers; catheters; vessels; space fillingimplants; implants for retention of hearing aids; implants for externalfixation; and also intrauterine devices (IUDs); and bioelectronicdevices such as intracochlear or intracranial electronic devices.

In some embodiments, the gradient bioceramics of the present applicationmay be used in restoration of human femoral necrosis, hip joint or toothdefects.

Hereinafter, the invention will be illustrated in more details by thefollowing examples with reference to the drawings for betterunderstanding of various aspects and advantages of the invention.However, it should be understood that the examples below arenon-limiting and are only illustrative of some of the embodiments of thepresent application.

EXAMPLE

Reagents and Apparatus

powdery titanium, purity: 95-99.4%, Shanghai Huijing Sub-Nanometer NewMaterials Co., Ltd.

CaHPO₄.2H₂O, purity: >99%, Shanghai Rebone Biomaterials Co., Ltd.

CaCO₃, purity: >99%, Shanghai Rebone Biomaterials Co., Ltd.

rare earth oxides, analytical pure, Shanghai Yuelong New Materials Co.,Ltd.

hydroxyapatite, purity: >99%, Shanghai Rebone Biomaterials Co., Ltd.

titanium alloy TC4, medical titanium materials, Foshan Nanxiang SpecialSteels Co., Ltd.

soya alkyds, Shanghai Rebone Biomaterials Co., Ltd.

TJ-HL-5000 5 kW CO₂ lasers, manufactured by Wuhan Unitylaser Inc.

TJ-LTM-VI five-axis three axes linkage laser processing numericalcontrol machine, manufactured by Tianjin Polytechnic University

JKF-6 laser broadband scan mirror, manufactured by Wuhan Unitylaser Inc.

Effects of Contents of Rare Earth Oxide on Phase Structure, Structureand Morphology, and Cracking Sensitivity of Bioceramic Coating

The tests were carried out at 0.2%, 0.4%, 0.6%, 0.8% and 1.0% of rareearth oxide, respectively. The test results showed that the content ofcatalytically synthesized hydroxyapatite and β-calcium phosphate reachedthe climax when the content of the rare earth oxide was up to 0.4 to0.6%, while the content of catalytically synthesized hydroxyapatite andβ-calcium phosphate began to decrease when the content of the rare earthoxide was up to 0.8%. In conclusion, the content of the rare earth oxidehas a significant effect on the formation of bioactive hydroxyapatiteand β-calcium phosphate. When the content of the rare earth oxide was upto 0.4 to 0.6%, the content of catalytically synthesized hydroxyapatiteand β-calcium phosphate reached the climax. The structure of thebioceramic coating comprising a rare earth oxide is significantly finerthan that comprising no rare earth oxide. The fined structure isbeneficial to increase the mechanical properties of the bioceramiccoating. The cracking sensitivity of the bioceramic coating comprising arare earth oxide is lower while that comprising no rare earth oxide ishigher.

Optimization of Technological Parameters of Broadband Laser Cladding

The studies on thermodynamics and kinetics showed that only bycontrolling the technological parameters of laser cladding canhydroxyapatite (HA) be formed. Therefore, in order to ensure the effectsof the present application, the technological parameters of lasercladding were optimized by inventors.

In order to obtain calcium and phosphor based bioceramic coatingcomprising HA in the cladding coating and to ensure good bonding betweenthe coating and the substrate, appropriate technological parameters oflaser cladding must be chosen.

Upon investigation it has been discovered that controlling a relativelylow output power of laser and a relatively high scanning rate are thekeys to obtain the bioceramic coating comprising calcium phosphate.However, if the output power is too low or the scanning rate is toohigh, the substrate and the cladding material will not be melted or willbe only partly melted, which leads to an unfirm bonding between thecladding layer and the substrate and therefore affects the bondingstrength.

Therefore, in the experiment the optimal technological parameters oflaser cladding were determined by changing the output power P and thescanning rate V. In particular, first of all, the spot size D and thescanning rate V were fixed while the output power P was changed. Thenthe spot size D and the output power P were fixed while the scanningrate V was changed. The optimal technological parameters of lasercladding were determined by analyzing the macro morphology,microstructure and microhardness.

1. Determination of Output Power P

The spot size D and the scanning rate V were fixed while the outputpower P was changed. First of all, a range of the output power wasapproximately determined. After several experiments, the range of thebroadband laser output power was preliminarily determined as 2.0 to 3.0kW through carefully observing the bonding conditions of the coating andthe substrate and the quality of the coating surface. The test schemewas designed as shown in Table 1.

TABLE 1 Technological Parameters of Broadband Laser Cladding GradientBioceramic Coating Output Power P Scanning Rate V Spot Size D Sample No.(kW) (mm/min) (mm × mm) 111 2.1 145 16 × 2 112 2.3 145 16 × 2 113 2.5145 16 × 2 114 2.7 145 16 × 2 115 2.9 145 16 × 2(1) Effects of Output Power on Structure of Composite Ceramic Coating

In the present experimental conditions, it was observed that the surfaceof sample No. 111 prepared with low power exhibits as melted beads andno bioceramic coating was formed. Due to the low output power, laserenergy absorbed by unit area of the sample, i.e., specific energy E_(b)was too low, such that no molten poor was formed on the surface of thetitanium alloy. The surface of sample No. 112 was relatively smooth anda bioceramic coating was formed. Bioceramic coatings were also formed onthe surfaces of sample Nos. 113-115. However, the surface qualitiesbecame worse from sample No. 113 to sample No. 115, in which the surfacequality of sample No. 115 was the worst. Due to a gradual increase inthe laser output power, laser energy absorbed by unit area of thesample, i.e., specific energy E_(b) gradually increased too, such thatthe temperature of the melt in the molten pool gradually increased,which led to an increase in the tension gradient on the surface of themolten poor dominated by the temperature gradient. The higher thetension gradient on the molten pool surface is, the more vigorously theconvection of the melts in the molten pool, which causes the surfacequality gradually becomes worse after solidification andcrystallization.

The substrate structure in the bioceramic coating of sample No. 112exhibits as cellular crystals, on which exists white fine particles andlocally exists aggregated white clusters of particles. The structure ofthe bioceramic coating is compact. There are fewer gaps in thebioceramic coating.

More gaps start to appear in the bioceramic coating of sample No. 113.Upon careful observation, some white ultrafine microparticlesdistributed in the bioceramic coating can be seen. With the energyspectrum and electron microprobe analysis, the white ultrafinemicroparticles are determined to be mainly Ti and Ca enriched oxides.The existence of the white ultrafine microparticles can improve thetoughness of the bioceramic coating.

Even more gaps appear in the microstructure of the bioceramic coating ofsample No. 114. The compactness of the microstructure became worse.

Some gaps in the bioceramic coating of sample No. 115 has linked up witheach other, forming large holes or cracks. The structure inevitablylowers the mechanical properties of the bioceramic coating.

In view of the above, along with an increase in the output power P, thestructural compactness of the bioceramic coating lowers, because thesintering temperature of the ceramics increases due to the increase ofthe output power. Along with an increase in the sintering temperature,the crystal grains forming the ceramics gradually grow gradually. At thesame time, angularities of the crystal grains become smooth and smallcrystal grains bonded to each other to form larger crystal grains. Atthis moment glassy liquid phase at the grain boundary fills the gapsamong the crystal grains and bonds small crystal grains. Small crystalgrains grow further and glassy liquid phase formed along with theincrease in temperature further fills the gaps. As such, the growth ofcrystal grains and filling of the liquid phase recycle continuously andfinally form ceramics by sintering.

Different from conventional sintering technologies, the laser claddingprocess is a rapid heating and rapid cooling process. When the outputpower is relatively high, i.e., the sintering temperature is relativelyhigh, the particle size of the formed crystal grains is relatively largeand the gaps formed due to failure to be filled by the liquid phase isrelatively large as well. On the other hand, when the output power isrelatively high, the thermal stress produced during the sinteringprocess is relatively high, which would readily result in relativelylarge holes and cracks. The bioceramic coating of the presentapplication is required to have certain porosity to enable bone tissuesgrowing into the holes.

According to the above experimental results, when the output power P=2.5kW, the surface of the prepared ceramics has certain compactness as wellas certain porosity. Therefore, the output power P=2.5 kW is an optimaltechnological parameter.

(2) Effects of Output Power on Porosity of Composite Ceramic Coating

With IAS-4 quantitative image analysis system, planar porosity ofbioceramic coatings of sample Nos. 112-115 was assayed, respectively.The results are shown in Table 2.

The specific procedures are described as follows. First of all, imagesof the bioceramic coating were collected. Gray value images were treatedwith shadow correction, image enhancement and the like in order toobserve the gaps more clearly. Secondly, image thresholding segmentationwas carried out. The area percent of the gaps was measured after binaryimage processing was conducted. Finally, porosities at differentlocations on the bioceramic coating were measured. The mean value of theporosities was calculated.

TABLE 2 Test Results of Porosities (%) of Different Samples Sample No.112 113 114 115 Porosity (%) 5 7 17 21

According to the results shown in Table 2, along with an increase in theoutput power P, the porosity in the bioceramic coating increasesgradually. When P=2.3 kW, as in sample No. 112, the porosity is thesmallest. When P=2.9 kW, as in sample No. 115, the porosity in thebioceramic coating is the largest.

Microhardness of bioceramic coatings of sample Nos. 112 and 115 weremeasured, respectively. The result showed that the microhardness ofbioceramic coating of sample No. 112 is larger than that of sample No.115 because the structure of the bioceramic coating of sample No. 112 iscompact and the porosity thereof is low. In contrast, the structure ofthe bioceramic coating of sample No. 115 is not compact and the porositythereof is higher, which inevitably leads to a decrease in microhardnessof the bioceramic coating. Therefore, regardless of porosity orhardness, the output power P=2.5 kW is an optimal parameter.

2. Determination of Scanning Rate V

The output power was fixed while the scanning rate was changed. The testscheme was designed as shown in Table 3.

TABLE 3 Technological Parameters of Broadband Laser Cladding GradientBioceramic Coating Output Power P Scanning Rate V Spot Size D Sample No.(kW) (mm/min) (mm × mm) 211 2.5 120 16 × 2 212 2.5 130 16 × 2 213 2.5140 16 × 2 214 2.5 150 16 × 2

According to the results, among the samples tested, the bioceramiccoating sample No. 211 has the largest gaps, in which some gaps linkedup with each other to form a line, leading to the worst structuralcompactness of the bioceramic coating. Meanwhile, among the samplestested, the bioceramic coating sample No. 214 has the smallest gaps andthe best structural compactness.

Upon determining the optimal output power, the structure and morphologyof the prepared bioceramic coatings improved significantly. The effectof the scanning rate on the surface morphology of the ceramics is not soremarkable as that of the output power. Along with an increase inscanning rate, the structural compactness of the ceramics increaseswhile the porosity of the ceramics decreases. Due to an increase inscanning rate, the residence time of light beams is relatively short,i.e., the sintering time becomes shortened. The crystal grains werecooled rapidly before growing such that the crystal grains were finedand the compactness of the crystal grains was increased. Moreover, whenthe scanning rate is relatively high, the power density on the surfaceof the materials becomes lower, resulting in a decrease in thermalstress such that the resultant holes and cracks would be reduced.Therefore, the increase in scanning rate will result in the increase inthe compactness, the strength and the hardness. When the scanning rateV=150 mm/min, the compactness of the ceramics is relatively high and thebonding between the ceramics and the substrate is good.

In view of the above study results and analysis, the optimaltechnological parameters of broadband laser cladding are laser outputpower P=2.5 kW, scanning rate V=150 mm/min, and spot size D=16 mm×2 mm.

Implant Tests in Mature Dog's Femurs

The bioceramic composite coatings were manufactured into strip samplesin 12 mm×3 mm×3 mm. The samples were subject to high temperature steamsterilization over 30 min at 126° C. Three mature and healthy dogs eachwith a weight of about 25 kg were selected. After anaesthetized, each ofthe three dogs was implanted with five samples, respectively, in theleft and right femurs. From proximal part to the distal part of thefemurs, the samples were in turn designated as 1#, 2#, 3#, 4# and 5#.The implant durations were one and a half months, three months and sixmonths, respectively. Over each duration a duplicate of each sample wasimplanted. The dogs were sacrificed without suffering before removingthe samples. The femoral parts in which samples were implanted wereremoved, fixed in 20% formalin, embedded with PMMA, sectioned andstained with Toluidine Blue. The sectioned tissues were observed withlow power and high power microscopes.

Example 1

Gradient Bioceramic Coating

The gradient bioceramic coating was prepared with 60 to 0% by weight ofpowdery titanium having a particle size of 40 μm and 40 to 100% byweight of powdery composite ceramics having a particle size of 36 μm,wherein the powdery composite ceramics were prepared by adding 0.6% byweight of a rare earth oxide CeO₂ having a particle size of 4 μm intopowdery ceramics which are obtained by mixing 78% by weight ofCaHPO₄.2H₂O and 22% by weight of CaCO₃.

A first gradient layer prepressed on the surface of a titanium alloy TC4was prepared by mixing and grinding 60% by weight of powdery titaniumand 40% by weight of powdery composite ceramics. A second gradient layerwas prepared by mixing and grinding 30% by weight of powdery titaniumand 70% by weight of powdery composite ceramics. A third gradient layerwas prepared by mixing and grinding 100% by weight of powdery compositeceramics.

Broadband Laser Cladding Method of Making the Gradient BioceramicCoating

The powdery ceramics and a rare earth oxide CeO₂ were mixed and groundover 3 hours to give a first mixture. The first mixture and powderytitanium were mixed and ground over 3 hours for thorough mixing to givea coating powder. The obtained coating powder was then mixed with 3 mLof soya alkyd, and the resulting mixture was prepressed on the surfaceof a titanium alloy TC4 with a pressure of 50 kg/cm². The thickness ofthe prepressed coating layer was 0.5 mm. The broadband laser claddingwas carried out with TJ-HL-5000 5 kW CO₂ lasers, TJ-LTM-VI five-axisthree axes linkage laser processing numerical control machine, and KF-6laser broadband scan mirror. The technological parameters of broadbandlaser cladding are 2.5 kW of output power P, 150 min/min of scanningrate V, and 16 mm×2 mm of spot size D. First of all, a first gradientlayer was cladded on the surface of a titanium alloy TC4 and thencleaned the residues on the surface and washed the surface. The obtainedcoating powder was prepressed on the surface of the titanium alloy TC4.A second gradient layer was cladded on the surface of the titanium alloyTC4 and then cleaned the residues on the surface and washed the surface.The obtained coating powder was prepressed on the surface of thetitanium alloy TC4. A third gradient layer was cladded on the surface ofthe titanium alloy TC4 to give a bioceramic coating on the surface ofthe titanium alloy TC4.

Example 2

Gradient Bioceramic Coating

The gradient bioceramic coating was prepared with 60 to 0% by weight ofpowdery titanium having a particle size of 20 μm, and 40 to 100% byweight of powdery composite ceramics having a particle size of 30 μm,wherein the powdery composite ceramics are prepared by adding 0.4% byweight of a rare earth oxide Y₂O₃ having a particle size of 1 μm intopowdery ceramics which are obtained by mixing 72% by weight ofCaHPO₄.2H₂O and 28% by weight of CaCO₃.

Each gradient layer prepressed on the surface of a titanium alloy TC4was identical to that in Example 1.

Broadband Laser Cladding Method of Making the Gradient BioceramicCoating

The powdery ceramics and a rare earth oxide Y₂O₃ were mixed and groundover 3 hours to give a first mixture. The first mixture and powderytitanium were mixed and ground over 3 hours for thorough mixing to givea coating powder. The obtained coating powder was then mixed with 3 mLof soya alkyd, and the resulting mixture was prepressed on the surfaceof a titanium alloy TC4 with a pressure of 50 kg/cm². The thickness ofthe prepressed coating layer was 0.4 mm. The broadband laser claddingwas carried out with TJ-HL-5000 5 kW CO₂ lasers, TJ-LTM-VI five-axisthree axes linkage laser processing numerical control machine and KF-6laser broadband scan mirror. The technological parameters of broadbandlaser cladding are 2.1 kW of output power P, 120 mm/min of scanning rateV, and 16 mm×1 mm of spot size D. First of all, a first gradient layerwas cladded on the surface of a titanium alloy TC4 and then cleaned theresidues on the surface and washed the surface. The obtained coatingpowder was prepressed on the surface of the titanium alloy TC4. A secondgradient layer was cladded on the surface of the titanium alloy TC4 andthen cleaned the residues on the surface and washed the surface. Theobtained coating powder was prepressed on the surface of the titaniumalloy TC4. A third gradient layer was cladded on the surface of thetitanium alloy TC4 to give a bioceramic coating on the surface of thetitanium alloy TC4.

Example 3

Gradient Bioceramic Coating

The gradient bioceramic coating was prepared with 60 to 0% by weight ofpowdery titanium having a particle size of 80 μm and 40 to 100% byweight of powdery composite ceramics having a particle size of 50 μm,wherein the powdery composite ceramics are prepared by adding 0.8% byweight of a rare earth oxide La₂O₃ having a particle size of 5 μm intopowdery ceramics which are obtained by mixing 80% by weight ofCaHPO₄.2H₂O and 20% by weight of CaCO₃.

Each gradient layer prepressed on the surface of a titanium alloy TC4was identical to that in Example 1.

Broadband Laser Cladding Method of Making the Gradient BioceramicCoating

The powdery ceramics and a rare earth oxide La₂O₃ were mixed and groundover 3 hours to give a first mixture. The first mixture and powderytitanium were mixed and ground over 3 hours for thorough mixing to givea coating powder. The obtained coating powder was then mixed with 3 mLof soya alkyd, and the resulting mixture was prepressed on the surfaceof a titanium alloy TC4 with a pressure of 50 kg/cm². The thickness ofthe prepressed coating layer was 0.6 mm. The broadband laser claddingwas carried out with TJ-HL-5000 5 kW CO₂ lasers, TJ-LTM-V1 five-axisthree axes linkage laser processing numerical control machine and KF-6laser broadband scan mirror. The technological parameters of broadbandlaser cladding are 2.9 kW of output power P, 200 mm/min of scanning rateV, and 30 mm×4 mm of spot size D. First of all, a first gradient layerwas cladded on the surface of a titanium alloy TC4 and then cleaned theresidues on the surface and washed the surface. The obtained coatingpowder was prepressed on the surface of the titanium alloy TC4. A secondgradient layer was cladded on the surface of the titanium alloy TC4 andthen cleaned the residues on the surface and washed the surface. Theobtained coating powder was prepressed on the surface of the titaniumalloy TC4. A third gradient layer was cladded on the surface of thetitanium alloy TC4 to give a bioceramic coating on the surface of thetitanium alloy TC4.

Example 4

The gradient bioceramic coating prepared in Example 2 (the coatingcomprises 0.4% of Y₂O₃) and a gradient bioceramic coating comprising noY₂O₃ were implanted into femurs of a mature and healthy dog (using themethod described in the Implant Tests in Mature Dog's Femurs in thepresent application). No physiological responses such as allergy,rejection and pathologic changes were observed at week 4, week 8 andweek 24. No symptoms such as obvious fibrous capsules, chronicinflammation, degeneration of tissue morphology, and tissue necrosiswere observed on the tissue sections. The gradient bioceramic coatingcomprising 0.4% of Y₂O₃ was bonded to new bone tissues at week 4 andthere were no gaps between the bone tissues and the coating. Thegradient bioceramic coating comprising no Y₂O₃ was not bonded to newbone tissues even after growing for 24 weeks.

Comparative Example 1

The gradient bioceramic coating prepared in Chinese patent applicationNo. 200510200011.5 (the coating comprises 0.4% of Y₂O₃) was implantedinto femurs of a mature and healthy dog. No physiological responses suchas allergy, rejection and pathologic changes were observed at week 6,week 12 and week 24. No symptoms such as obvious fibrous capsules,chronic inflammation, degeneration of tissue morphology, and tissuenecrosis were observed on the tissue sections. X-ray films showed thatthe thickness of hyperosteogeny increased gradually and the ceramiccoating bonded to new bone tissues at week 6.

The above test results demonstrate that the bioceramic coating of thepresent application has better bioactivity and biocompatibility. Theduration for bonding to bone tissues can be decreased by about 2 weeks.

Theoretically speaking, the higher content of powdery titanium is in thefirst gradient layer in the bioceramic coating, the betterphysicochemical compatibility exhibits between the coating and thetitanium alloy TC4. However, compared with the bioceramic coating ofChinese patent application No. 200510200011.5, the content of powderytitanium in the first gradient layer in the bioceramic coating of thepresent application is decreased by 10%. The test results show thatwhere the content of titanium is 60%, the bonding between the coatingand the substrate is still a metallurgical bonding and the interfacialbonding strength between the coating and the substrate is higher. Inview of the above, this ratio does not constitute an influence on thephysicochemical compatibility between the coating and the titanium alloyTC4.

In addition, since the content of powdery titanium in the third gradientlayer in the bioceramic coating of Examples 1-3 is zero, the content ofhydroxyapatite (HA) produced during the laser cladding process isrelatively high. The test results show that the content of pure HAproduced during laser cladding 100% of powdery composite ceramics isabout 20%, such that the content of HA in the bioceramic coating ishigher. Therefore, the bioactivity and biocompatibility of thebioceramic coating of the present application are significantly highercompared with that of Chinese patent application No. 200510200011.5.

Compared with the state of the prior art, the present applicationutilizes broadband laser cladding techniques and more reasonablegradient design so that the obtained bioceramic coating has less cracksor holes, higher hardness, and better toughness. No amorphous phasesexist in the coating. Moreover, because the content of powdery titaniumin the third gradient layer which contacts with the human body is zerowhile the content of HA is higher, the bioactivity and biocompatibilityof the obtained product are significantly increased. Therefore, theobtained product can be used in restoration of human femoral necrosis,hip joint or tooth defects and would not induce a rejection. Therestoration period of the obtained product is shorter (compared withthat of the bioceramic coating of Chinese patent application No.200510200011.5, the restoration period is shortened by about 1 to 3weeks depending on specific conditions of an individual).

The effects of the addition of a rare earth oxide into the powderyceramics of Examples 1-3 are to catalytically synthesize hydroxyapatiteand β-calcium phosphate during the laser cladding process, increase themechanical properties of the bioceramic coating, and decrease thecracking sensitivity of the bioceramic coating. The bioceramic coatingcomprising a rare earth oxide (e.g., CeO₂ or La₂O₃) also has theanticoagulation effects and can prevent carcinogenesis. Moreover,because there are more micropores formed on the surface of the coating,more channels are provided for the bone tissues to grow into thecoating.

Example 5

Gradient Bioceramic Coating

The gradient bioceramic coating was prepared with 60 to 0% by weight ofpowdery titanium having a particle size of 40 μm, 40 to 70% by weight ofpowdery composite ceramics having a particle size of 36 μm, and 0 to 50%by weight of hydroxyapatite having a particle size of 15 μm, wherein thepowdery composite ceramics were prepared by adding 0.6% by weight of arare earth oxide Y₂O₃ having a particle size of 4 μm into powderyceramics which are obtained by mixing 78% by weight of CaHPO₄.2H₂O and22% by weight of CaCO₃.

A first gradient layer prepressed on the surface of a titanium alloy TC4was prepared by mixing and grinding 60% by weight of powdery titaniumand 40% by weight of powdery composite ceramics. A second gradient layerwas prepared by mixing and grinding 30% by weight of powdery titaniumand 70% by weight of powdery composite ceramics. A third gradient layerwas prepared by mixing and grinding 50% by weight of powdery compositeceramics and 50% by weight of hydroxyapatite (HA).

Broadband Laser Cladding Method of Making the Gradient BioceramicCoating

The powdery ceramics and a rare earth oxide Y₂O₃ were mixed and groundover 3 hours to give a first mixture. The first mixture and powderytitanium were mixed and ground over 3 hours for thorough mixing to givea first coating powder. The powdery ceramics and a rare earth oxide Y₂O₃were mixed and ground over 3 hours to give a second mixture. The secondmixture and hydroxyapatite were mixed and ground over 3 hours forthorough mixing to give a second coating powder. The obtained firstcoating powder was mixed with 3 mL of soya alkyd, and the resultingmixture was prepressed on the surface of a titanium alloy TC4 with apressure of 50 kg/cm². The thickness of the prepressed coating layer was0.5 mm. The broadband laser cladding was carried out with TJ-HL-5000 5kW CO₂ lasers, TJ-LTM-VI five-axis three axes linkage laser processingnumerical control machine, and KF-6 laser broadband scan mirror. Thetechnological parameters of broadband laser cladding are 2.5 kW ofoutput power P, 150 min/min of scanning rate V, and 16 mm×2 mm of spotsize D. First of all, a first gradient layer was cladded on the surfaceof a titanium alloy TC4 and then cleaned the residues on the surface andwashed the surface. The obtained first coating powder was prepressed onthe surface of the titanium alloy TC4. A second gradient layer wascladded on the surface of the titanium alloy TC4 and then cleaned theresidues on the surface and washed the surface. The obtained secondcoating powder was prepressed on the surface of the titanium alloy TC4.A third gradient layer was cladded on the surface of the titanium alloyTC4 to give a bioceramic coating on the surface of the titanium alloyTC4.

Example 6

Gradient Bioceramic Coating

The gradient bioceramic coating was prepared with 60 to 0% by weight ofpowdery titanium having a particle size of 20 μm, 40 to 70% by weight ofpowdery composite ceramics having a particle size of 30 μm, and 0 to 50%by weight of hydroxyapatite having a particle size of 10 μm, wherein thepowdery composite ceramics are prepared by adding 0.4% by weight of arare earth oxide CeO₂ having a particle size of 1 μm into powderyceramics which are obtained by mixing 72% by weight of CaHPO₄.2H₂O and28% by weight of CaCO₃.

Each gradient layer prepressed on the surface of a titanium alloy TC4was identical to that in Example 5.

Broadband Laser Cladding Method of Making the Gradient BioceramicCoating

The powdery ceramics and a rare earth oxide CeO₂ were mixed and groundover 3 hours to give a first mixture. The first mixture and powderytitanium were mixed and ground over 3 hours for thorough mixing to givea first coating powder. The powdery ceramics and a rare earth oxide CeO₂were mixed and ground over 3 hours to give a second mixture. The secondmixture and hydroxyapatite were mixed and ground over 3 hours forthorough mixing to give a second coating powder. The obtained firstcoating powder was mixed with 1 mL of soya alkyd, and the resultingmixture was prepressed on the surface of a titanium alloy TC4 with apressure of 50 kg/cm². The thickness of the prepressed coating layer was0.54 mm. The broadband laser cladding was carried out with TJ-HL-5000 5kW CO₂ lasers, TJ-LTM-VI five-axis three axes linkage laser processingnumerical control machine, and KF-6 laser broadband scan mirror. Thetechnological parameters of broadband laser cladding are 2.1 kW ofoutput power P, 120 mm/min of scanning rate V, and 16 mm×1 mm of spotsize D. First of all, a first gradient layer was cladded on the surfaceof a titanium alloy TC4 and then cleaned the residues on the surface andwashed the surface. The obtained first coating powder was prepressed onthe surface of the titanium alloy TC4. A second gradient layer wascladded on the surface of the titanium alloy TC4 and then cleaned theresidues on the surface and washed the surface. The obtained secondcoating powder was prepressed on the surface of the titanium alloy TC4.A third gradient layer was cladded on the surface of the titanium alloyTC4 to give a bioceramic coating on the surface of the titanium alloyTC4.

Example 7

Gradient Bioceramic Coating

The gradient bioceramic coating was prepared with 60 to 0% by weight ofpowdery titanium having a particle size of 80 μm, 40 to 70% by weight ofpowdery composite ceramics having a particle size of 50 μm, and 0 to 50%by weight of hydroxyapatite having a particle size of 30 μm, wherein thepowdery composite ceramics are prepared by adding 0.8% by weight of arare earth oxide La₂O₃ having a particle size of 5 μm into powderyceramics which are obtained by mixing 80% by weight of CaHPO₄.2H₂O and20% by weight of CaCO₃.

Each gradient layer prepressed on the surface of a titanium alloy TC4was identical to that in Example 5.

Broadband Laser Cladding Method of Making the Gradient BioceramicCoating

The powdery ceramics and a rare earth oxide La₂O₃ were mixed and groundover 3 hours to give a first mixture. The first mixture and powderytitanium were mixed and ground over 3 hours for thorough mixing to givea first coating powder. The powdery ceramics and a rare earth oxideLa₂O₃ were mixed and ground over 3 hours to give a second mixture. Thesecond mixture and hydroxyapatite were mixed and ground over 3 hours forthorough mixing to give a second coating powder. The obtained firstcoating powder was mixed with 5 mL of soya alkyd, and the resultingmixture was prepressed on the surface of a titanium alloy TC4 with apressure of 50 kg/cm². The thickness of the prepressed coating layer was0.6 mm. The broadband laser cladding was carried out with TJ-HL-5000 5kW CO₂ lasers, TJ-LTM-VI five-axis three axes linkage laser processingnumerical control machine, and KF-6 laser broadband scan mirror. Thetechnological parameters of broadband laser cladding are 2.9 kW ofoutput power P, 200 mm/min of scanning rate V, and 30 mm×4 mm of spotsize D. First of all, a first gradient layer was cladded on the surfaceof a titanium alloy TC4 and then cleaned the residues on the surface andwashed the surface. The obtained first coating powder was prepressed onthe surface of the titanium alloy TC4. A second gradient layer wascladded on the surface of the titanium alloy TC4 and then cleaned theresidues on the surface and washed the surface. The obtained secondcoating powder was prepressed on the surface of the titanium alloy TC4.A third gradient layer was cladded on the surface of the titanium alloyTC4 to give a bioceramic coating on the surface of the titanium alloyTC4.

Example 8

The gradient bioceramic coating prepared in Example 5 (the coatingcomprises 0.6% of Y₂O₃) and a gradient bioceramic coating comprising noY₂O₃ were implanted into femurs of a mature and healthy dog (using themethod described in the Implant Tests in Mature Dog's Femurs in thepresent application). No physiological responses such as allergy,rejection and pathologic changes were observed at week 1, week 4 andweek 8. No symptoms such as obvious fibrous capsules, chronicinflammation, degeneration of tissue morphology, and tissue necrosiswere observed on the tissue sections. The gradient bioceramic coatingcomprising 0.6% of Y₂O₃ was bonded to new bone tissues at week 1 andthere were no gaps between the bone tissues and the coating. Thegradient bioceramic coating comprising no Y₂O₃ was not bonded to newbone tissues even after growing for 8 weeks.

Comparative Example 2

The gradient bioceramic coating prepared in Chinese patent applicationNo. 200510200011.5 (the coating comprises 0.6% of Y₂O₃) was implantedinto femurs of a mature and healthy dog. No physiological responses suchas allergy, rejection and pathologic changes were observed at week 6,week 12 and week 24. No symptoms such as obvious fibrous capsules,chronic inflammation, degeneration of tissue morphology, and tissuenecrosis were observed on the tissue sections. X-ray films showed thatthe thickness of hyperosteogeny increased gradually and the ceramiccoating bonded to new bone tissues at week 6.

The above test results demonstrate that the bioceramic coating of thepresent application has better bioactivity and biocompatibility. Theduration for bonding to bone tissues can be decreased by about 5 weeks.

Theoretically speaking, the higher content of powdery titanium is in thefirst gradient layer in the bioceramic coating, the betterphysicochemical compatibility exhibits between the coating and thetitanium alloy TC4. However, compared with the bioceramic coating ofChinese patent application No. 200510200011.5, the content of powderytitanium in the first gradient layer in the bioceramic coating of thepresent application is decreased by 10%. The test results show thatwhere the content of titanium is 60%, the bonding between the coatingand the substrate is still a metallurgical bonding and the interfacialbonding strength between the coating and the substrate is higher. Inview of the above, this ratio does not constitute an influence on thephysicochemical compatibility between the coating and the titanium alloyTC4.

In addition, since the content of powdery titanium in the third gradientlayer in the bioceramic coating of Examples 5-7 is zero, the content ofhydroxyapatite (HA) produced during the laser cladding process isrelatively high. The addition of 50% of HA results in an even highercontent of HA in the coating. Therefore, the bioactivity andbiocompatibility of the bioceramic coating of the present applicationare significantly higher compared with that of Chinese patentapplication No. 200510200011.5. The results of a series of tests showthat the content of pure HA produced during laser cladding 100% ofpowdery composite ceramics is about 20%, while the content of pure HAproduced during laser cladding 50% of powdery composite ceramics plus50% of HA can reach about 60%.

Compared with the state of the prior art, the present applicationutilizes broadband laser cladding techniques and more reasonablegradient design so that the obtained bioceramic coating has less cracksor holes, higher hardness, and better toughness. No amorphous phasesexist in the coating. Moreover, because the content of powdery titaniumin the third gradient layer which contacts with the human body is zerowhile the content of HA is higher, the bioactivity and biocompatibilityof the obtained product are significantly increased. Therefore, theobtained product can be used in restoration of human femoral necrosis,hip joint or tooth defects and would not induce a rejection. Therestoration period of the obtained product is shorter (compared withthat of the bioceramic coating of Chinese patent application No.200510200011.5, the restoration period is shortened by about 3 to 5weeks depending on specific conditions of an individual).

The effects of the addition of a rare earth oxide into the powderyceramics of Examples 5-7 are to catalytically synthesize hydroxyapatiteand β-calcium phosphate during the laser cladding process, increase themechanical properties of the bioceramic coating, and decrease thecracking sensitivity of the bioceramic coating. The bioceramic coatingcomprising a rare earth oxide (e.g., CeO₂ or La₂O₃) also has theanticoagulation effects and can prevent carcinogenesis. Moreover,because there are more micropores formed on the surface of the coating,more channels are provided for the bone tissues to grow into thecoating.

Example 9

Gradient Bioceramic Coating Comprising CeO₂

The gradient bioceramic coating was prepared with 70 to 10 kg of powderytitanium having a particle size of 40 μm, and 30 to 90 kg of powderycomposite ceramics having a particle size of 36 μm, wherein the powderycomposite ceramics were prepared by adding 0.6 kg of a rare earth oxideCeO₂ having a particle size of 4 μm into powdery ceramics which areobtained by mixing 78 kg of CaHPO₄.2H₂O and 22 kg of CaCO₃.

A first gradient layer prepressed on the surface of a titanium alloy TC4was prepared by mixing and grinding 70 kg of powdery titanium and 30 kgof powdery composite ceramics. A second gradient layer was prepared bymixing and grinding 40 kg of powdery titanium and 60 kg of powderycomposite ceramics. A third gradient layer was prepared by mixing andgrinding 10 kg of powdery titanium and 90 kg of powdery compositeceramics.

Method of Making the Gradient Bioceramic Coating Comprising CeO₂

The powdery ceramics and a rare earth oxide CeO₂ were mixed and groundover 3 hours to give a first mixture. The first mixture and powderytitanium were mixed and ground over 3 hours for thorough mixing to givea coating powder. The obtained coating powder was mixed with 3 mL ofsoya alkyd, and the resulting mixture was prepressed on the surface of atitanium alloy TC4 with a pressure of 50 kg/cm². The thickness of theprepressed coating layer was 0.5 mm. The broadband laser cladding wascarried out with TJ-HL-5000 5 kW CO₂ lasers, TJ-LTM-VI five-axis threeaxes linkage laser processing numerical control machine, and KF-6 laserbroadband scan mirror. The technological parameters of broadband lasercladding are 2.5 kW of output power P, 150 mm/min of scanning rate V,and 16 mm×2 mm of spot size D. First of all, a first gradient layer wascladded on the surface of a titanium alloy TC4 and then cleaned theresidues on the surface and washed the surface. The obtained coatingpowder was prepressed on the surface of the titanium alloy TC4. A secondgradient layer was cladded on the surface of the titanium alloy TC4 andthen cleaned the residues on the surface and washed the surface. Theobtained coating powder was prepressed on the surface of the titaniumalloy TC4. A third gradient layer was cladded on the surface of thetitanium alloy TC4 to give a bioceramic coating on the surface of thetitanium alloy TC4.

Example 10

Gradient Bioceramic Coating Comprising CeO₂

The gradient bioceramic coating was prepared with 75 to 15 kg of powderytitanium having a particle size of 20 μm, and 35 to 85 kg of powderycomposite ceramics having a particle size of 30 μm, wherein the powderycomposite ceramics were prepared by adding 0.4 kg of a rare earth oxideCeO₂ having a particle size of 1 μm into powdery ceramics which areobtained by mixing 72 kg of CaHPO₄.2H₂O and 28 kg of CaCO₃.

A first gradient layer prepressed on the surface of a titanium alloy TC4was prepared by mixing and grinding 75 kg of powdery titanium and 25 kgof powdery composite ceramics. A second gradient layer was prepared bymixing and grinding 45 kg of powdery titanium and 55 kg of powderycomposite ceramics. A third gradient layer was prepared by mixing andgrinding 15 kg of powdery titanium and 85 kg of powdery compositeceramics.

Method of Making the Gradient Bioceramic Coating Comprising CeO₂

The powdery ceramics and a rare earth oxide CeO₂ were mixed and groundover 3 hours to give a first mixture. The first mixture and powderytitanium were mixed and ground over 3 hours for thorough mixing to givea coating powder. The obtained coating powder was mixed with 1 mL ofsoya alkyd, and the resulting mixture was prepressed on the surface of atitanium alloy TC4 with a pressure of 50 kg/cm². The thickness of theprepressed coating layer was 0.4 mm. The broadband laser cladding wascarried out with TJ-HL-5000 5 kW CO₂ lasers, TJ-LTM-VI five-axis threeaxes linkage laser processing numerical control machine, and KF-6 laserbroadband scan mirror. The technological parameters of broadband lasercladding are 2.0 kW of output power P, 100 mm/min of scanning rate V,and 16 mm×1 mm of spot size D. First of all, a first gradient layer wascladded on the surface of a titanium alloy TC4 and then cleaned theresidues on the surface and washed the surface. The obtained coatingpowder was prepressed on the surface of the titanium alloy TC4. A secondgradient layer was cladded on the surface of the titanium alloy TC4 andthen cleaned the residues on the surface and washed the surface. Theobtained coating powder was prepressed on the surface of the titaniumalloy TC4. A third gradient layer was cladded on the surface of thetitanium alloy TC4 to give a bioceramic coating on the surface of thetitanium alloy TC4.

Example 11

Gradient Bioceramic Coating Comprising CeO₂

The gradient bioceramic coating was prepared with 80 to 20 kg of powderytitanium having a particle size of 80 μm, and 20 to 80 kg of powderycomposite ceramics having a particle size of 50 μm, wherein the powderycomposite ceramics were prepared by adding 0.8 kg of a rare earth oxideCeO₂ having a particle size of 5 μm into powdery ceramics which areobtained by mixing 80 kg of CaHPO₄.2H₂O and 20 kg of CaCO₃.

A first gradient layer prepressed on the surface of a titanium alloy TC4was prepared by mixing and grinding 80 kg of powdery titanium and 20 kgof powdery composite ceramics. A second gradient layer was prepared bymixing and grinding 50 kg of powdery titanium and 50 kg of powderycomposite ceramics. A third gradient layer was prepared by mixing andgrinding 20 kg of powdery titanium and 80 kg of powdery compositeceramics.

Method of Making the Gradient Bioceramic Coating Comprising CeO₂

The powdery ceramics and a rare earth oxide CeO₂ were mixed and groundover 3 hours to give a first mixture. The first mixture and powderytitanium were mixed and ground over 3 hours for thorough mixing to givea coating powder. The obtained coating powder was mixed with 5 mL ofsoya alkyd, and the resulting mixture was prepressed on the surface of atitanium alloy TC4 with a pressure of 50 kg/cm². The thickness of theprepressed coating layer was 0.6 mm. The broadband laser cladding wascarried out with TJ-HL-5000 5 kW CO₂ lasers, TJ-LTM-VI five-axis threeaxes linkage laser processing numerical control machine, and KF-6 laserbroadband scan mirror. The technological parameters of broadband lasercladding are 3.0 kW of output power P, 200 mm/min of scanning rate V,and 30 mm×4 mm of spot size D. First of all, a first gradient layer wascladded on the surface of a titanium alloy TC4 and then cleaned theresidues on the surface and washed the surface. The obtained coatingpowder was prepressed on the surface of the titanium alloy TC4. A secondgradient layer was cladded on the surface of the titanium alloy TC4 andthen cleaned the residues on the surface and washed the surface. Theobtained coating powder was prepressed on the surface of the titaniumalloy TC4. A third gradient layer was cladded on the surface of thetitanium alloy TC4 to give a bioceramic coating on the surface of thetitanium alloy TC4.

Example 12

The gradient bioceramic coating prepared in Example 9 (the coatingcomprises 0.6% of CeO₂) and a gradient bioceramic coating comprising noCeO₂ were implanted into femurs of a mature and healthy dog (using themethod described in the Implant Tests in Mature Dog's Femurs in thepresent application). No physiological responses such as allergy,rejection and pathologic changes were observed at week 6, week 12 andweek 24. No symptoms such as obvious fibrous capsules, chronicinflammation, degeneration of tissue morphology, and tissue necrosiswere observed on the tissue sections. The gradient bioceramic coatingcomprising 0.6% of CeO₂ was bonded to new bone tissues at week 6 andthere were no gaps between the bone tissues and the coating. Thegradient bioceramic coating comprising no CeO₂ was not bonded to newbone tissues even after growing for 24 weeks. This shows that thegradient bioceramic coating comprising 0.6% of CeO₂ has good bioactivityand biocompatibility.

Compared with the state of the prior art, the bioceramic coatings ofExamples 9-11 have less cracks or holes, higher hardness and bettertoughness. No amorphous phases exist in the coatings. The product can beimplanted into the human body as a substitute for bone and bone joint.The product has the anticoagulation effects and can preventcarcinogenesis while would not induce a rejection.

The present application utilizes a concept of gradient design and usesbroadband laser cladding techniques to directly cladCaHPO₄.2H₂O+CaCO₃+Ti powder on the surface of a titanium alloy (i.e.,one-step process) so as to increase the bonding strength of theinterface and endow the coating with good biocompatibility. The Gaussianenergy distribution of broadband laser becomes a rectangular energydistribution after being treated with broadband scan mirror such thatthe energy distribution becomes uniform. Such a rectangular energydistribution can make the temperature distribution of a molten pooluniform and make the temperature in the central area of the molten pooldecreasing in a gradient manner such that the cracking sensitivitydecreases. Moreover, the temperature gradient of the molten pool edgescan form an appropriate surface tension field and play a role instirring the melt so as to make alloy elements distribute uniformly. Inaddition, the width of the cladding can be increased and the lappingtimes can be reduced so that the productivity will be increased.

The addition of CeO₂ into the powdery ceramics in Example 9-11 plays arole in catalytically synthesize hydroxyapatite and β-calcium phosphateand the obtained bioceramic coating also has the anticoagulation effectsand can prevent carcinogenesis. Furthermore, more micropores are formedon the surface of the bioceramic coating comprising CeO₂ than thoseformed on the surface of the bioceramic coating comprising Y₂O₃ suchthat more channels are provided for the bone tissues to grow into thecoating.

Example 13

Gradient Bioceramic Coating Comprising La₂O₃

The gradient bioceramic coating was prepared with 70 to 10% by weight ofpowdery titanium having a particle size of 40 μm, and 30 to 90% byweight of powdery composite ceramics having a particle size of 36 μm,wherein the powdery composite ceramics were prepared by adding 0.6% byweight of a rare earth oxide La₂O₃ having a particle size of 4 μm intopowdery ceramics which are obtained by mixing 78% by weight ofCaHPO₄.2H₂O and 22% by weight of CaCO₃.

A first gradient layer prepressed on the surface of a titanium alloy TC4was prepared by mixing and grinding 70% by weight of powdery titaniumand 30% by weight of powdery composite ceramics. A second gradient layerwas prepared by mixing and grinding 40% by weight of powdery titaniumand 60% by weight of powdery composite ceramics. A third gradient layerwas prepared by mixing and grinding 10% by weight of powdery titaniumand 90% by weight of powdery composite ceramics.

Method of Making the Gradient Bioceramic Coating Comprising La₂O₃

The powdery ceramics and a rare earth oxide La₂O₃ were mixed and groundover 3 hours to give a first mixture. The first mixture and powderytitanium were mixed and ground over 3 hours for thorough mixing to givea coating powder. The obtained coating powder was mixed with 3 mL ofsoya alkyd, and the resulting mixture was prepressed on the surface of atitanium alloy TC4 with a pressure of 50 kg/cm². The thickness of theprepressed coating layer was 0.5 mm. The broadband laser cladding wascarried out with TJ-HL-5000 5 kW CO₂ lasers, TJ-LTM-VI five-axis threeaxes linkage laser processing numerical control machine, and KF-6 laserbroadband scan mirror. The technological parameters of broadband lasercladding are 2.5 kW of output power P, 150 mm/min of scanning rate V,and 16 mm×2 mm of spot size D. First of all, a first gradient layer wascladded on the surface of a titanium alloy TC4 and then cleaned theresidues on the surface and washed the surface. The obtained coatingpowder was prepressed on the surface of the titanium alloy TC4. A secondgradient layer was cladded on the surface of the titanium alloy TC4 andthen cleaned the residues on the surface and washed the surface. Theobtained coating powder was prepressed on the surface of the titaniumalloy TC4. A third gradient layer was cladded on the surface of thetitanium alloy TC4 to give a bioceramic coating on the surface of thetitanium alloy TC4.

Example 14

Gradient Bioceramic Coating Comprising La₂O₃

The gradient bioceramic coating was prepared with 75 to 15% by weight ofpowdery titanium having a particle size of 20 μm, and 25 to 85% byweight of powdery composite ceramics having a particle size of 30 μm,wherein the powdery composite ceramics were prepared by adding 0.4% byweight of a rare earth oxide La₂O₃ having a particle size of 1 μm intopowdery ceramics which are obtained by mixing 72% by weight ofCaHPO₄.2H₂O and 28% by weight of CaCO₃.

A first gradient layer prepressed on the surface of a titanium alloy TC4was prepared by mixing and grinding 75% by weight of powdery titaniumand 25% by weight of powdery composite ceramics. A second gradient layerwas prepared by mixing and grinding 45% by weight of powdery titaniumand 55% by weight of powdery composite ceramics. A third gradient layerwas prepared by mixing and grinding 15% by weight of powdery titaniumand 85% by weight of powdery composite ceramics.

Method of Making the Gradient Bioceramic Coating Comprising La₂O₃

The powdery ceramics and a rare earth oxide La₂O₃ were mixed and groundover 3 hours to give a first mixture. The first mixture and powderytitanium were mixed and ground over 3 hours for thorough mixing to givea coating powder. The obtained coating powder was mixed with 1 mL ofsoya alkyd, and the resulting mixture was prepressed on the surface of atitanium alloy TC4 with a pressure of 50 kg/cm². The thickness of theprepressed coating layer was 0.4 mm. The broadband laser cladding wascarried out with TJ-HL-5000 5 kW CO₂ lasers, TJ-LTM-V1 five-axis threeaxes linkage laser processing numerical control machine, and KF-6 laserbroadband scan mirror. The technological parameters of broadband lasercladding are 2.1 kW of output power P, 120 mm/min of scanning rate V,and 16 mm×1 mm of spot size D. First of all, a first gradient layer wascladded on the surface of a titanium alloy TC4 and then cleaned theresidues on the surface and washed the surface. The obtained coatingpowder was prepressed on the surface of the titanium alloy TC4. A secondgradient layer was cladded on the surface of the titanium alloy TC4 andthen cleaned the residues on the surface and washed the surface. Theobtained coating powder was prepressed on the surface of the titaniumalloy TC4. A third gradient layer was cladded on the surface of thetitanium alloy TC4 to give a bioceramic coating on the surface of thetitanium alloy TC4.

Example 15

Gradient Bioceramic Coating Comprising La₂O₃

The gradient bioceramic coating was prepared with 80 to 20% by weight ofpowdery titanium having a particle size of 80 μm, and 20 to 80% byweight of powdery composite ceramics having a particle size of 50 μm,wherein the powdery composite ceramics were prepared by adding 0.8% byweight of a rare earth oxide La₂O₃ having a particle size of 5 μm intopowdery ceramics which are obtained by mixing 80% by weight ofCaHPO₄.2H₂O and 20% by weight of CaCO₃.

A first gradient layer prepressed on the surface of a titanium alloy TC4was prepared by mixing and grinding 80% by weight of powdery titaniumand 20% by weight of powdery composite ceramics. A second gradient layerwas prepared by mixing and grinding 50% by weight of powdery titaniumand 50% by weight of powdery composite ceramics. A third gradient layerwas prepared by mixing and grinding 20% by weight of powdery titaniumand 80% by weight of powdery composite ceramics.

Method of Making the Gradient Bioceramic Coating Comprising La₂O₃

The powdery ceramics and a rare earth oxide La₂O₃ were mixed and groundover 3 hours to give a first mixture. The first mixture and powderytitanium were mixed and ground over 3 hours for thorough mixing to givea coating powder. The obtained coating powder was mixed with 5 mL ofsoya alkyd, and the resulting mixture was prepressed on the surface of atitanium alloy TC4 with a pressure of 50 kg/cm². The thickness of theprepressed coating layer was 0.6 mm. The broadband laser cladding wascarried out with TJ-HL-5000 5 kW CO₂ lasers, TJ-LTM-VI five-axis threeaxes linkage laser processing numerical control machine, and KF-6 laserbroadband scan mirror. The technological parameters of broadband lasercladding are 2.9 kW of output power P, 200 mm/min of scanning rate V,and 30 mm×4 mm of spot size D. First of all, a first gradient layer wascladded on the surface of a titanium alloy TC4 and then cleaned theresidues on the surface and washed the surface. The obtained coatingpowder was prepressed on the surface of the titanium alloy TC4. A secondgradient layer was cladded on the surface of the titanium alloy TC4 andthen cleaned the residues on the surface and washed the surface. Theobtained coating powder was prepressed on the surface of the titaniumalloy TC4. A third gradient layer was cladded on the surface of thetitanium alloy TC4 to give a bioceramic coating on the surface of thetitanium alloy TC4.

Example 16

The gradient bioceramic coating prepared in Example 14 (the coatingcomprises 0.4% of La₂O₃) and a gradient bioceramic coating comprising noLa₂O₃ were implanted into femurs of a mature and healthy dog (using themethod described in the Implant Tests in Mature Dog's Femurs in thepresent application). No physiological responses such as allergy,rejection and pathologic changes were observed at week 6, week 12 andweek 24. No symptoms such as obvious fibrous capsules, chronicinflammation, degeneration of tissue morphology, and tissue necrosiswere observed on the tissue sections. The gradient bioceramic coatingcomprising 0.6% of CeO₂ was bonded to new bone tissues at week 6 andthere were no gaps between the bone tissues and the coating. Thegradient bioceramic coating comprising no La₂O₃ was not bonded to newbone tissues even after growing for 24 weeks. This shows that thegradient bioceramic coating comprising 0.4% of La₂O₃ has goodbioactivity and biocompatibility.

Compared with the state of the prior art, the bioceramic coatings ofExamples 13-15 have less cracks or holes, higher hardness and bettertoughness. No amorphous phases exist in the coatings. The product can beimplanted into the human body as a substitute for bone and bone joint.The product has the anticoagulation effects and can preventcarcinogenesis while would not induce a rejection.

The present application utilizes a concept of gradient design and usesbroadband laser cladding techniques to directly cladCaHPO₄.2H₂O+CaCO₃+Ti powder on the surface of a titanium alloy (i.e.,one-step process) so as to increase the bonding strength of theinterface and endow the coating with good biocompatibility. The Gaussianenergy distribution of broadband laser becomes a rectangular energydistribution after being treated with broadband scan mirror such thatthe energy distribution becomes uniform. Such a rectangular energydistribution can make the temperature distribution of a molten pooluniform and make the temperature in the central area of the molten pooldecreasing in a gradient manner such that the cracking sensitivitydecreases. Moreover, the temperature gradient of the molten pool edgescan form an appropriate surface tension field and play a role instirring the melt so as to make alloy elements distribute uniformly. Inaddition, the width of the cladding can be increased and the lappingtimes can be reduced so that the productivity will be increased.

The addition of La₂O₃ into the powdery ceramics in Example 13-15 plays arole in catalytically synthesize hydroxyapatite and β-calcium phosphateand the obtained bioceramic coating also has the anticoagulation effectsand can prevent carcinogenesis. Furthermore, more micropores are formedon the surface of the bioceramic coating comprising La₂O₃ than thoseformed on the surface of the bioceramic coating comprising Y₂O₃ suchthat more channels are provided for the bone tissues to grow into thecoating.

These and other changes can be made in light of the above-detaileddescription. In general, in the following claims, the terms used shouldnot be construed to be limiting to the specific embodiments disclosed inthe specification and the claims, but should be construed to include allsystems, devices and/or methods that operate in accordance with theclaims. Accordingly, the invention is not limited by the disclosure, butinstead its scope is to be determined entirely by the following claims.

All of the above U.S. patents, U.S. patent application publications,U.S. patent applications, foreign patents, foreign patent applicationsand non-patent publications referred to in this specification and/orlisted in the Application Data Sheet, are incorporated herein byreference, in their entirety.

From the foregoing it will be appreciated that, although specificembodiments of the invention have been described herein for purposes ofillustration, various modifications may be made without deviating fromthe spirit and scope of the invention. Accordingly, the invention is notlimited except as by the appended claims.

What is claimed is:
 1. A gradient bioceramic coating, wherein thegradient bioceramic coating is prepared with powdery titanium, andpowdery composite ceramics, wherein the powdery composite ceramics iscomposed of powdery ceramics obtained by mixing CaHPO₄.2H₂O and CaCO₃and a rare earth oxide, wherein the gradient bioceramic coatingcomprises a first gradient layer, a second gradient layer and a thirdgradient layer and wherein the first gradient layer and the secondgradient layer are composed of powdery titanium and powdery compositeceramics, and the third gradient layer consists of powdery compositeceramics.
 2. The gradient bioceramic coating of claim 1, wherein on thebasis of weight percent, the gradient bioceramic coating is preparedwith about 60 to 0% of powdery titanium and about 40 to 100% of powderycomposite ceramics, wherein the powdery composite ceramics are composedof powdery ceramics obtained by mixing about 67 to 85% by weight ofCaHPO₄.2H₂O and about 15 to 33% by weight of CaCO₃ and about 0.2 to 1.0%by weight of a rare earth oxide.
 3. The gradient bioceramic coating ofclaim 1, wherein the particle size of the powdery titanium is in therange of about 10 to 90 μm, the particle size of the powdery compositeceramics is in the range of about 20 to 60 μm, and the particle size ofthe rare earth oxide is in the range of about 0.1 to 10 μm.
 4. Thegradient bioceramic coating of claim 3, the particle size of the powderytitanium is about 40 μm, the particle size of the powdery compositeceramics is about 36 μm, and the particle size of the rare earth oxideis about 4 μm.
 5. The gradient bioceramic coating of claim 1, whereinthe rare earth oxide is selected from the group consisting of yttriumoxide (Y₂O₃), yttrium europium oxide ((Y,Eu)₂O₃), europium oxide(Eu₂O₃), lanthanum oxide (La₂O₃), cerous oxide (Ce₂O₃), ceric oxide(CeO₂), terbium oxide (Tb₄O₇) (including cerium terbium oxide((Ce,Tb)_(x)O_(y)), lanthanum cerium terbium oxide((La,Ce,Tb)_(x)O_(y)), lanthanum phosphate activated by cerium andterbium: Ce(III), Tb(III)), samarium oxide (Sm₂O₃), neodminu oxide(Nd₂O₃), dysprosium oxide (Dy₂O₃), erbium oxide (Er₂O₃), ytterbium oxide(Yb₂O₃) and cerium zirconium oxide ((Ce,Zr)O₂).
 6. The gradientbioceramic coating of claim 5, wherein the rare earth oxide is selectedfrom the group consisting of lanthanum oxide (La₂O₃), ceric oxide (CeO₂)and yttrium oxide (Y₂O₃).
 7. A method of making a gradient bioceramiccoating of claim 1, comprising (a) mixing and grinding powdery ceramicsand a rare earth oxide to give a first mixture, and then mixing andgrinding the first mixture and powdery titanium to give a coatingpowder; (b) mixing the coating powder and an adhesive to give a secondmixture, and then prepressing the second mixture on the surface of atitanium alloy TC4; and (c) with broadband laser cladding techniques,cladding the second mixture to give a first gradient layer on thesurface of the titanium alloy TC4, and then prepressing the firstcoating powders the surface of the titanium alloy TC4 and cladding togive a second gradient layer, and then prepressing the second coatingpowders the surface of the titanium alloy TC4 and cladding to give athird gradient layer, so as to obtain the gradient bioceramics on thesurface of the titanium alloy TC4.
 8. The method of claim 7, wherein thetechnological parameters of broadband laser cladding are about 2.0 to3.0 kW of output power P, about 100 to 200 mm/min of scanning rate V,and about 16 to 30 mm×1 to 4 mm of spot size D.
 9. The method of claim7, wherein the thickness of the layer prepressed on the surface of thetitanium alloy TC4 is in the range of about 0.2 to 0.8 mm.
 10. Themethod of claim 7, wherein the pressure of prepressing the coatingpowders is in the range of about 40 to 60 kg/cm².
 11. A method torestore defects in human sclerous tissues or substitute human scleroustissues, comprising implanting a gradient bioceramic coating of claim 1.